Hydraulic hammer



p 1967 E. F. KLESSIG HYDRAULIC HAMMER Filed April 1, 1965 5 Sheets-Sheet 3 W 8 .4 Z Z 4 4 7 9 0% 9 Q J WM H J m v 0 6 2/ \K. v z w w w f y 1i I I? 1 ill I m 3% F H [I v Q m a r 0 .H w A J if}? i .m M w 7 lwU. 1, a l 7 /1 Z w 6W1 1/ W E. F. KLESSIG HYDRAULIC HAMMER Sept. 5, 1967 5 Sheets-Sheet 3 Filed April 1, 1965 United States Patent 3,339,644 HYDRAULIC HAMMER Ernst F. Klessig, Racine, Wis., assignor to Racine Hydraulics & Machinery, Inc., a corporation of Wiscousin Filed Apr. 1, 1965, Ser. No. 444,742 12 Claims. (Cl. 173-127) ABSTRACT OF THE DISCLOSURE A fluid actuated hammer including a casing having a bore, a piston reciprocally mounted within the bore, the piston having first valve means formed thereon, a hammer movable with the piston to strike a tool, second valve means reciprocally mounted within the bore and operative in conjunction with the first valve means to control passage of fluid to the piston to drive the hammer against the tool and to relieve fluid pressure on the piston to allow the hammer to be returned to a starting position, a means including the first valve means for reciprocating the second valve means and a means for relieving excessive pressures within the casing when the second valve means is switching from a position wherein the hammer is driven and a position wherein the piston is returned to its original starting position.

Summary of the invention The principal object of this invention is to provide a new and improved hydraulic hammer.

More specifically, it is an object of the invention to provide a hydraulic hammer wherein all the control elements are contained Within the hammer casing to provide a portable and compact construction.

Another object of the invention is to provide a hydraulic hammer wherein the control valving does not require a special, separate, mechanical actuator.

Another object of the invention is to provide a hydraulic hammer wherein the control valving does not require a special, separate, mechanical actuator, and wherein the valving is arranged with respect to the piston so as to substantially reduce the number of fluid passages within the housing.

Another object of the invention is the provision in a hydraulic hammer of a new and improved bumper mechanism for cushioning the return of the piston actuated hammer.

Another object of the invention is the provision in a hydraulic hammer of a new and improved resilient tool mounting wherein spring mean-s are confined within the hammer casing to preclude interference therewith by objects in the environment in which the hydraulic hammer is operated, thereby resulting in a hydraulic hammer that may be used with greater safety.

Another object of the invention is to provide a control valve for a hydraulic hammer that is arranged concentrically about the piston so as to minimize the space requirements for the control valve.

Another object of the invention is the provision in a control valve for a hydraulic hammer of means for shifting the control valve to various positions through the use of surfaces of differing areas.

Other objects and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings.

Description of the drawings "ice mer shown in FIGURE 1, and showing one stage of a cycle of the operation of the device;

FIGURE 3 is a fragmentary vertical section of the hydraulic hammer, and showing another stage in a cycle of the operation of the device;

FIGURE 4 is yet another fragmentary vertical section of the hydraulic hammer, and showing still another stage in a cycle of the operation of the device;

FIGURE 5 is still another fragmentary vertical section of the hydraulic hammer, and showing a further stage in a cycle of the operation of the device;

FIGURE 6 is a vertical section taken approximately along the line 66 of FIGURE 4, and showing a portion of the duct work in a device made according to themvention;

FIGURE 7 is a fragmentary horizontal section taken approximately along the line 7-7 of FIGURE 5, and showing a portion of a control valve operator of a device made according to the invention;

FIGURE 8 is a fragmentary horizontal section taken approximately along the line 8-8 of FIGURE 5, and showing another portion of a control valve operator in a device made according to the invention; and

FIGURE 9 is a fragmentary horizontal section taken approximately along the line 9-9 of FIGURE 2, and showing a portion of a manual control valve for a hydraulic hammer made according to the invention.

Detailed description An exemplary form of the invention is generally designated 20, as seen in FIGURE 1. The hydraulic hammer comprises an upper casing section 22 having a flange 24 on its lower end. A lower casing section 26 has an inturncd end 27 on its lower extremity, and a flange 28 on its upper end. The flange 28 is suitably constructed so as to mate with the upper casing flange 24. The two casing sections are secured together by suitable fastening means, such as bolts 30 and nuts 32.

As best seen in FIGURE 2, the lower casing section 26 further comprises a bore 34. Within the upper end of the bore 34 is a sleeve 36, within which an impacting hammer is received for reciprocating movement relative thereto, as will be seen hereinafter. Abutting the lower end of the sleeve 36 is a second sleeve, generally designated 38, which is of stepped construction. The sleeve 38 comprises a pair of sections, the largest section 40, having a dimension substantially equal to that of the bore 34, while the smaller section 42 has a diameter substantially less than that of the bore 34. The smaller section 42 of the sleeve 38 additionally carries a keyway 44 in which is received a key 46 which is mounted in a threaded aperture 48 in the inturncd section 27 of the lower casing 26. Suitable springs 50 are interposed between the inturncd end portion 27 and the enlarged section 40 of the sleeve 38 so as to bias the latter against the lower edge of the sleeve 36.

As is apparent from FIGURE 2, the springs 50 are about the smaller section 42 of the sleeve 38 and are contained only within the lower casing section 26. This feature is extremely desirable as it lends an added safety factor to the device. It will be appreciated that during operation of the hammer, the springs 50 will, on occasion, be subject to flexing, as when the hammer is withdrawn from the work. In prior art devices, comparable springs are externally exposed and thus subject to interference by objects within the environment in which the hammer is being used. Such interference could cause the interfering object to be propelled by the springs against the operator of the hammer or other workmen and bystanders and possibly result in injury to such persons. Furthermore, in such prior art constructions, there is the possibility of portions of the workmens apparel or even the limbs of the workmen being caught in such springs which could result in injury thereto. However, in a construction according to the invention, the springs 50 are totally enclosed, thus wholly eliminating all such possibilities.

The sleeve 38 is also provided with an irregularly shaped bore 52 for reception of the complementary shaped end 54 of a tool 56. Intermediate the ends of the tool 56 is provided a collar 58 to limit movement of the tool within the bore 52 in one direction. To limit movement of the tool 56 within the bore 52 in the other direction, there is provided a latch 60 which is pivotally mounted at 62 to the inturned end 27 of the casing 26. The latch 60 includes an extension portion 64 arranged in the path of the tool collar 58. A manually operable lever 66 is mounted on the latch 60, such that the latter may be selectively manipulated to move the extension 64 out of the path of the tool collar 58, so that the tool may be removed from the hammer mechanism. A plunger 68 is mounted in a bore 70 in the casing 26 and is biased by a spring 72, also received in the bore 70, against the latch 60 so as to normally maintain the extension 64 in the path of the collar 58.

The upper casing section 22 is provided with an inlet 74 for hydraulic fluid and an outlet 76 for the same (see FIGURES 1 and 2). As will be seen hereinafter, a gastype pressure accumulator 78, which may be of conventional construction, communicates with the inlet 74, while a similar accumulator 80 communicates with the outlet 76. The accumulators 78 and 80 serve to smooth pressure pulses within the hydraulic fluid.

The inlet 74 includes a threaded bore 82 (see FIGURE 2) which may receive a suitable hose and fitting 84 connected to a source of hydraulic oil under pressure. The threaded bore 82 terminates in a chamber 86 having a pair of branch conduits 88 and 90. Aligned with the conduit 90 is a bore 91 in which is disposed a tubular valve 92. On the end of the tubular valve 92 remote from the conduit 90 is a plurality of gear teeth 94 which are meshed with a spur gear 96 disposed within a bore 98. The spur gear 96 is mounted on a shaft 100 which is journalled in a plug 102 for the bore 98 (see FIGURE 9). The plug 102 is maintained in a sealing relation with the bore 98 by securing means such a screws 103. Additionally, suitable sealing means 104 are disposed between the bore 98 and the plug 102 for reasons that will be seen hereinafter. A handle, or manual operator, 106 is mounted on the end of the shaft 100 and may be rotated to cause rotation of the spur gear 96 and thus reciprocal movement of the tubular valve 92 within the bore 91 and the conduit 90. A spring 108 is interposed between the upper end of the tubular valve 92 and a plug 110 which seals the upper end of the bore 91. The tubular valve 92 is provided with a hollow center 112 to permit passage of pressurized fluid therethrough to the upper end of the tubular valve member 92. Such a construction is desirable as the pressurized fluid within the chamber 86 exerts a substantial force on the bottom of the tubular valve 92, which tends to force the tubular valve 92 upwardly. However, the hollow center 112 permits the fluid to pass to the upper end of the valve 92 to exert an equalizing downward force on the upper end of the tubular valve member 92.

The upper casing 22 is provided with a stepped bore 113 in which a piston 114 is received for reciprocation relative thereto as seen in FIGURE 2. An upper section 116 of the bore 113 is slightly enlarged to receive an enlarged piston head 118. The piston head 118 has a pair of operating surfaces 120 and 122 oppositely disposed thereon. The uppermost surface 120 has a significantly larger size or surface area than does the lower operating surface 122. An annular port 124 is formed in the enlarged section 116 of the bore 113 and is in communication with the inlet conduit 88. Additionally, a channel 126, which is periodically placed in communication with the inlet 74 terminates in an annular port 127 in the bore 113 above the large piston operating surface 120.

Because of the difference in effective area of the two piston operating surfaces and 122, in the absence of pressurized fluid in the channel 126 and the port 127 exerting a force on the large operating surface 120, pressurized fluid flowing from the inlet 74 through the conduit 88 will pass from the port 124 along the side of the piston 114 in the enlarged section 116 of the bore 113 to exert an upward force on the small operating surface 122 of the piston 114 to cause the latter to move upwardly. However, when the channel 126 is supplied with pressurized fluid, which will ultimately act downwardly on the large surface 120 of the piston 114, a greater total force will be exerted on that surface by virtue of its larger area, thus forcing the piston downwardly.

In the upper end of the bore 113 is placed a bumper 128 having an outwardly flared upper portion 130 (see FIGURES 2 and 6). The outwardly flared portion 130 is seated on an appropriate recess 132 in the upper end of the bore 113. A spring 134 is interposed between the bumper 128 and a sealing plug 136 threaded into the upper end of the bore 113. As best seen in FIGURE 6, an annular port 138 is placed in the upper end of the bore 113 between the bumper 128 and the plug 136. A conduit 140 connects the ports 138 to the port 124 and ultimately to the inlet 74, thus providing a path for pressurized fluid to the space in the bore 113 between the bumper 128 and the plug 136, to bias the bumper 128 downwardly. The lower end of the bumper 128 is positioned within the bore 113 so as to abut the end of the piston 114 when the latter is in its uppermost position. The purpose of this construction is twofold. Firstly, by virtue of its hydraulic and spring biasing, the bumper 128 will tend to dissipate the kinetic energy of the piston 114 imposed thereon by a positive contact therewith if such should occur. Secondly, the nature of the operation of a hydraulic hammer is such that extremely high pressure pulses may exist within the fluid above the piston during such times as the channel 126 is not in communication with the inlet 74 or the outlet 76. The pressure of such pulses may be greater than the inlet pressure and are relieved by movement of the bumper 128.

The lower end of the bore 113 is provided with a greatly enlarged section 142 [for reception of a reciprocal spool valve 144 (see FIGURE 2). Within the enlarged bore section 142, are three annular outlet ports 146, 148 and 150, the ports 146 and 150 serving to equalize pressure on the opposite ends of the spool valve 144, which communicate with each other, with the outlet accumulator 80 and with the outlet 76 by means of a channel 151. Placed between the outlet ports 148 and 150, respectively, are an annular port 154 in communication with the channel 126 and an inlet port 152 communicating with a chamber 153 which is in fluid communication with the conduit 90, and thus the inlet 74. The inlet port 152 also communicates with the inlet accumulator 78 by virtue of the connection of the latter to the chamber 153.

Formed on and extending about the outer periphery of the spool valve 144, is a first annular groove 156 arranged such that for one position of the spool valve 144 within the enlarged bore section 142, the inlet port 152 will communicate with the port :154 to direct pressurized fluid into the channel 126 and to the piston head 118. Additionally, the first annular groove 156 is arranged to be in continuous communication with the inlet port 152, and thus the inlet '74. Also formed on and extending about the periphery of the spool valve 144 is a second annular groove 158 which is placed on the spool valve 144 such that for another position of the spool valve 144 within the enlarged bore 142, the second annular groove 158 will permit communication between the port 154, and thus the channel 126, and the outlet port 148 to relieve the pressure exerted on the piston head 118.

The spool valve 144 includes a central bore 160 through which the piston 114 extends. The spool valve bore 160 together with the piston 114 defines a first annular duct 162 which is separated by a land 163 (FIGURE 3) from a second annular duct 164, which in turn is separated by a land 165 from a third annular duct 166. Apertures 167 permit fluid communication between the first annular passage 162 and the first annular groove 156 for purposes as will be seen hereinafter, while, by virtue of its location on the lower end of the spool valve 144, the third annular duct 166 is substantially continuously in communication with the outlet port 146.

To cause the spool valve 144 to reciprocate within the enlarged bore section 142, there are provided in opposite ends of the spool valve 144, a pair of groups of opposed bores 168 and 172. As best seen in FIGURE 7, the group of bores 168 comprise two bores, while the group of bores 172 comprise four such bores, as is seen in FIGURE 8. Pin 170 are placed within the group of bores 168 while pins 174 are placed within the group of bores 172. In the case of both the pin 170 and the pins 174, one end of each pin abuts a stationary portion of the casing, or the like. As seen in FIGURE 2, the group of bores 168 communicate directly with the first annular groove 156 while the group of bores 172 communicate with the second annular duct 164 in the spool valve 144 by means of a relieved portion 173 in the bore 160 of the spool valve 144. It will be appreciated that because of the opposed relation of the ends of the respective groups of bores 168 and 172 and by reason of the greater number of bores in the group 172, and thus the greater total surface area of the ends of the bores of the group, when pressure is directed to the group of bores 172 in the manner hereafter described and acts upon the surface at the ends of the bores, the spool valve 144 will be forced upwardly as seen in the various figures. On the other hand, when there is no pressure exerted against the ends of the group of bores 172, the pressure exerted against the ends of the group of bores 168 by virtue of the direct connection with the first annular groove 156, and thus the inlet port 152, will result in the spool valve 144 being forced downwardly.

To alternatively pressurize and relieve the group of bores 172, there is provided a first annular passage 176 on the piston 114 which is separated by a land 177 [from a second annular passage 178. The passages 176 and 178 on the piston 114 are arranged with respect to the ducts 162, 164 and 166 in the bore 160 of the spool valve 144 such that for one position (see FIGURE 3) of the piston 114 with respect to the spool valve 144, the first annular passage 176 permits fluid communication between the first annular duct 162 and the second annular duct 164, and thus the group of bores 172; while for another position (see FIGURE 5) of the piston with respect to the spool valve 144, the second annular passage 178 will permit fluid communication between the second annular duct 164, and thus the group of bores 172, and the third annular duct 166. These relationships may be respectively seen in FIG- URES 4 and 5.

Since the first annular duct 162 is in continuous communication with the inlet 74, it will be apparent that whenever the position of the annular passage 176 is such as to permit communication between the first annular duct 162, the second annular duct 164, and the group of bores 172, the spool valve 144 will be moved upwardly to be there maintained until the pressure is relieved. Furthermore, since the third annular duct 166 is in substantially continuous communication with the outlet, it will be apparent that whenever the second annular passage 178 permits communication between the second annular duct 164 and the third annular duct 166, the pressure exerted in the group of bores 172 will be relieved thus permitting the pressure exerted within the group of bores 168 to force the spool valve 144 downwardly.

The lower end of the enlarged bore section 142 is closed by a plug 180 held in place by suitable securing means such as bolts 182, as shown in FIGURE 3. The plug 180 is provided with a 'bore 184 through which the piston 114 extends. Near the lower end of the plug bore 184 is placed an annular port 186 which communicates by means of a conduit 188 with the outlet port 146. The annular port 186 collects the major portion of the fluid 1eak age between the piston 114and the plug 180 and directs such fluid to the outlet port 146 and ultimately to the out let 76. As a {further leakage precluding measure, beneath the annular port 186 there is provided suitable sealing means 192 between the plug 180 and the piston 114. Additional-1y, sealing means 190 are placed along the interface of the plug 180 and the upper casing member 22 to preclude leakage there'between.

As maybe seen from FIGURES 2 through 6 inclusive, the plug 180 is attached to the lower end of the upper casing member 22. Accordingly, that portion of the piston 114 that projects through the plug 180, etxends into'the lower casing section 26 and has attached thereto a hammer 194. As best seen in FIGURE 2, the piston 114 terminates in a conical end 196 which is received in a mating recess 198 within the hammer 194. To secure the hammer 194 to the piston 114, there is provided a threaded nut member 200 which is received in a threaded recess 202 within the hammer 194. The lower end of the nut 200 bears against a locking ring 204 which is seated in an annular groove 206 in the piston 114. By tightening the threaded nut member 200 against the locking ring 204, the hammer 194 is effectively locked against movement relative to the piston 114 and will move there- With within the sleeve 36 in the lower casing member 26.

The operation of the device is as follows. Turning first to FIGURE 2, if it is assumed that the inlet 74 is connected to a source of hydraulic oil under pressure and that the tubular valve 92 extends into the conduit thus precluding communication of the latter with the inlet 74,

pressurized fluid will flow through the conduit 88, the port 124, and the enlarged bore section 116 to the small operating surface 122 of the piston head 118, thus forcing the latter upwardly until it abuts the bumper 128. The piston will be maintained in this position until the valve 92 is opened. With the piston 114' in this position, the second annular passage 178 on the piston 114 will permit any pressurized oil in the group of bores 172 to flow to the outlet 146 through the relieved portion 173, the second annular duct 164, the second annular passage 178 and the third annular duct 166. Accordingly, the spool valve 144 will drop to its lowest position within the enlarged bore section 142 under the influence of gravity or will be driven to such position when the valve 92 is open by the admission of pressurized oil to the group of bores 168.

When the valve 92 is open, pressurized oil will flow from the inlet 74 to the enlarged surface of the piston via the conduit 90, the chamber 153, the inlet port 152, the first annular groove 156, the annular port 154, the channel 126, and the port 127 to drive the piston 114 and the hammer 194 downwardly such that the latter impacts upon the tool 56. The resulting position of the various elements is shown in FIGURE 3.

With the downward movement of the piston 114, fluid communication between the inlet 74 and the group of bores 172 is established via the conduit 90, the chamber 153, the inlet port 152, the first annular groove 156, the apertures 167, the first annular duct 162, the first annular passage 176, the second annular duct 164 and the relieved portion 173. Accordingly,-the spool valve 144 is driven upwardly to the position shown in FIGURE 4.

As a result, communication between the inlet 74 and the large operating surface 120 of the piston 118 is cut off and a new path of communication from the large piston operating surface 120 is established to the outlet -76 to relieve the pressure exerted on the former. This path of communication is established via port 127, channel 126, port 154, the second annular groove 158, the outlet port 148 and the channel 151. The relationship of the elements at this stage of the cycle is shown in FIGURE 4.

The resulting absence of pressure exerted on the large operating surface 120 of the piston 114 results in the latter being moved upwardly by the continual force exerted on the small operating surface 122 of the piston 114 by pressurized fluid directed thereagainst from the inlet 74 by conduit 88, port 124, and the enlarged bore section 116. With the upward movement of the piston 114, fluid communication is established between the group of bores 172 and the outlet 76 through the relieved portion 173, the first annular duct 164, the sec-nd annular groove 178, the outlet port 146 and the channel 151. The resulting relation between the various elements is shown in FIG- U-RE 5.

With the relieving of pressure on the ends of the group of bores 172 through the path just mentioned, the pressure continually exerted on the ends of the group of bores 168 will force the spool valve 144 downwardly until it returns to the position shown in FIGURE 2. Once again communication is established between the inlet 74 and the enlarged operating surface 120 of the piston 114 and the device initiates another cycle. This cycling will continue until the valve 92 is closed.

It will be apparent that the spool valve 144, at a point about midway between its etxreme lower and upper positions (see FIGURES 3 and 4, respectively), will not permit communication between the channel 126 and the inlet port 152 or the outlet port 148. In other words, channel 126 is temporarily blocked. Any pressure pulses in the hydraulic fluid above the piston 114 and within the channel 126 caused by the impact of the hammer 194 on the tool 56 will, however, be reduced to acceptable level of a magnitude approaching that of the inlet pressure by the yielding action of the movable bumper 128 and its communication with the inlet 74 via port 138, conduit 140, port 124, conduit 88 and chamber 86. Additionally, during the return of the piston 118 to its upper position, when the channel 126 is blocked, the pressure created by displacement of fluid by the surface 120 is dissipated by the yielding of the bumper 128.

It will further be observed from FIGURE 5 that the land 177 and the second annular passage 178 on the piston 114 are positioned with respect to the second and third annular ducts 162 and 164, respectively, such that pressure in the group of bores 172 is relieved through the path previously stated substantially before the piston 114 reaches its extreme upper position. This causes the spool valve 144 to shift downwardly prior to the time at which the piston 118 achieves its upper position. The piston 118 is thereby caused to decelerate to a stop at about the time it contacts the bumper 128, first by the pressure increase above the large operating surface 120 due to the blocking of the channel 126 by the spool valve 144 in the course of its movement, and secondly, by the subjection of the large operating surface 124 to inlet pressure when the spool valve 144 has substantially completed its movement prior to the time at which the pitson 118 reaches its upper position. Should the spool valve 144 stick slightly, the bumper mechanism will stop the piston and dissipate its kinetic energy without damage to the casing.

It will be appreciated that by selective adjustment of the valve 92, the pressure exerted on the enlarged operating surface 120 of the piston 114 can be regulated thus regulating the rapidity of reciprocation of the piston 114 and the hammer 194. Accordingly, the number of cycles through which the device progresses in any given period of time can be selectively adjusted.

From the foregoing, it will be apparent that a hydraulic hammer made according to the invention will be an extremely compact device by virtue of the arrangement of the valving with respect to the piston. This same construction provides a distinct advantage over various prior art devices by the elimination of a number of fluid paths within the hammer casing thereby eliminating costly boring in the casing to provide such fluid paths. Furthermore, the means for shifting the valve member in a hydraulic hammer according to the invention to control the action of the hammer does not require any special mechanical operators and accompanying linkages, thereby resulting in a simpler construction.

While such terms as conduit, channel, passage, duct and port have been used in the foregoing description in relation to the various elements, which use was necessitated by a desire to provide clarity in the foregoing description, it is intended that they be substantially synonymous and commonly definitive of any structure capable of passing a fluid, and not be limited to the specific illustrated structure with which they are associated.

Having disclosed a specific embodiment of my invention as required by 35 U.S.C. 112, I do not wish to be limited to the construction set forth, but rather, to have my invention construed according to its true spirit as set forth in the following claims.

I claim:

1. A hydraulic hammer comprising (a) a casing having a bore, an inlet port, a pair of connected outlet ports, and a channel,

(b) a piston mounted for reciprocation within said bore, said piston having a pair of opposed operating surfaces of differing size, said channel communicating at one end thereof with the larger of said operating surfaces, said inlet port communicating with the smaller of said operating surfaces, a portion of said piston bearing first and second separate passages,

(c) a hammer on one end of said piston,

(d) an annular spool valve within said casing and mounted about the passage bearing portion of said piston for reciprocating movement relative to both said casing and said piston, said spool valve having first and second annular grooves about its outer surface and positioned such that for one position of said spool valve within said casing, said first annular groove will connect said inlet port and the other end of said channel for fluid passage therethrough, and for another position of said spool valve within said casing said second annular groove will connect said other end of said channel to one of said outlet ports for fluid passage therebetween; said first annular groove further being positioned to be in communication with said inlet port for all positions of said spool valve within said housing; said spool valve further including first, second and third separate ducts formed in its inner surface, said first duct being in continuous communication with said first annular groove and thus said inlet port; said third duct being positioned to be in substantially continuous communication with the other of said pair of outlet ports; said first and second passages on said piston and said first, second and third ducts being arranged with respect to each other such that for one position of said spool valve relative to said piston, said first passage will establish fluid communication between said first and second ducts, and for another position of said spool valve relative to said piston, said second passage will establish communication between said second and third ducts,

(e) spool valve positioning means including a pair of opposed surface means of differing size on said spool valve, the largest of said pair of surface means being in communication with said second duct, the smallest of said pair of surface means being in communication with said first annular groove, whereby when said inlet port is connected to a source of fluid under pressure, said hammer will be cyclically reciprocatcd.

2. A fluid actuated hammer comprising (a) a casing having a bore, an inlet, an outlet and a channel,

(b) a piston within said bore and mounted for reciprotatiqn. W h n. said. ca g be n an mpa position and a return position, said channel communicating with said piston,

(c) a hammer attached to said piston,

(d) annular valve means about said piston and movable to a first position for connecting said channel to said inlet to supply fluid under pressure to said piston to move the latter from said return position to said impact position and movable to a position to connect said channel to said outlet whereby said piston may be moved to said return position,

(e) means for moving said piston to said return position, and

(f) means responsive to the position of said piston within the casing for cyclically moving said valve means to said pressure fluid supplying position.

3. The fluid actuated hammer of claim 2 wherein said piston has a pair of operating surfaces differing in size from each other, and wherein said piston moving means comprises a conduit for continuously directing fluid under pressure to the smaller of said operating surfaces.

4. The fluid actuated hammer of claim 2 wherein said annular valve means comprises a spool valve reciprocally mounted within said casing and wherein said connecting means comprises a pair of annular grooves on said spool valve.

5. The fluid actuated hammer of claim 2 wherein said piston has a pair of operating surfaces differing in size from one another and wherein said channel communicates with the larger of said pair of piston operating surfaces, said inlet further comprising an opening adapted to be connected to a source of fluid under pressure, a first conduit communicating between said opening and the smaller of said piston operating surfaces, a second conduit communicating between said opening and said annular valve means connecting means, and a valve member within said opening for selectively and adjustably permitting communication between said second conduit and said opening.

6. The fluid actuated hammer of claim 2, including bumper means in said bore adjacent said piston, said bumper means including an element having a portion positioned to abut said piston when the latter is in said return position, spring means resiliently biasing said element into said position, and means for directing fluid under pressure against said element to urge said element into said position.

7. A fluid actuated hammer comprising:

(a) a casing including a bore,

(b) a piston reciprocally mounted within said bore,

said piston including first valve means formed thereon,

(c) a hammer on said piston,

(d) second valve means reciprocally mounted within said bore and at least partially surrounding said valve means, said second valve means being operative to control the passage of fluid to said piston to cause said piston to reciprocate said hammer, and

(e) means including said first valve means for reciprocating said second valve means, said second valve means reciprocating means comprising a pair of fluid actuated surface means, one of said surface means of said pair having a greater area exposed to fluid than the other of said pair of surface means.

8. The fluid actuated hammer of claim 7 wherein said first valve means includes a first passage for periodically supplying fluid under pressure to said one of said surface means and a second passage for periodically relieving fluid pressure on said one of said surface means.

9. The fluid actuated hammer of claim 8 wherein said second valve means includes first duct means for continuously supplying fluid under pressure to said first passage and second duct means for connecting said one of said surface means alternatively to said first passage and to said second passage.

10. In a hydraulic hammer, the combination comprising:

(a) a casing having a bore; an inlet for receiving hydraulic fluid under pressure, and an outlet;

(b) a piston having an operating surface reciprocally mounted within said bore and a hammer movable with said piston;

(c) valve means movable between a first position wherein said inlet is in fluid communication with said operating surface to apply hydraulic fluid under pressure to said operating surface to move said piston in a first direction, and a second position wherein said operating surface is in fluid communication with said outlet to relieve fluid pressure on sad operating surface whereby said piston may be moved in a second direction opposite said first direction;

(d) means for moving said piston in said second direction; and

(e) yieldable means operative when said valve means is in transit moving from said second position to said first position to at least partially relieve hydraulic fluid pressure within said bore adjacent said operating surface when said piston is being moved in said second direction whereby a trapped column of hydraulic fluid cannot exist between said bore and said valve means when said piston is moving in said second direction and said operating surface is not in fluid communication with either of said inlet and said outlet.

11. The hydraulic hammer of claim 10 wherein said valve means comprises a reciprocal valve and said yieldable means comprises a movable element biased into an end of said bore adjacent said opertaing surface having a first surface in fluid communication with said bore and a second surface in continuous fluid communication with said inlet whereby when fluid pressure within said bore exceeds a predetermined level, said element will move against the bias and fluid pressure applied thereto from said inlet to relieve excessive pressure within said bore with said excessive pressure being transmitted by said element to said inlet.

12. The hydraulic hammer of claim 10 wherein a single channel provides for fluid communication between said operating surface and said valve means, said valve means comprising a single valve member for alternately connecting said inlet and said channel and said outlet and said channel.

References Cited UNITED STATES PATENTS 919,035 4/ 1909 Lane 91-299 1,807,787 6/1931 Jirnerson 91-299 1,827,647 10/1931 Galaz 173-162 2,180,034 11/1939 Charles l73133 2,672,847 3/1954 Bergmann 173127 3,204,534- 9/1965 Spannhake 173-127 FRED c. MATTERN, JR., Primary Examiner.

L. P. KESSLER, Assistant Examiner. 

1. A HYDRAULIC HAMMER COMPRISING (A) A CASING HAVING A BORE, AN INLET PORT, A PAIR OF CONNECTED OUTLET PORTS, AND A CHANNEL, (B) A PISTON MOUNTED FOR RECIPROCATION WITHIN SAID BORE, SAID PISTON HAVING A PAIR OF OPPOSED OPERATING SURFACES OF DIFFERING SIZE, SAID CHANNEL COMMUNICATING AT ONE END THEREOF WITH THE LARGER OF SAID OPERATING SURFACES, SAID INLET PORT COMMUNICATING WITH THE SMALLER OF SAID OPERATING SURFACES, A PORTION OF SAID PISTON BEARING FIRST AND SECOND SEPARATE PASSAGES, (C) A HAMMER ON ONE END OF SAID PISTON, (D) AN ANNULAR SPOOL VALVE WITHIN SAID CASING AND MOUNTED ABOUT THE PASSAGE BEARING PORTION OF SAID PISTON FOR RECIPROCATING MOVEMENT RELATIVE TO BOTH SAID CASING AND SAID PISTON, SAID SPOOL VALVE HAVING FIRST AND SECOND ANNULAR GROOVES ABOUT ITS OUTER SURFACE AND POSITIONED SUCH THAT FOR ONE POSITION OF SAID SPOOL VALVE WITHIN SAID CASING, SAID FIRST ANNULAR GROOVE WILL CONNECT SAID INLET PORT AND THE OTHER END OF SAID CHANNEL FOR FLUID PASSAGE THERETHROUGH, AND FOR ANOTHER POSITION OF SAID SPOOL VALVE WITHIN SAID CASING SAID SECOND ANNULAR GROOVE WILL CONNECT SAID OTHER END OF SAID CHANNEL TO ONE OF SAID OUTLET PORTS FOR FLUID PASSAGE THEREBETWEEN; SAID FIRST ANNULAR GROOVE FURTHER BEING POSITIONED TO BE IN COMMUNICATION WITH SAID INLET PORT FOR ALL POSITIONS OF SAID SPOOL VALVE WITHIN SAID HOUSING; SAID SPOOL VALVE FURTHER INCLUDING FIRST, SECOND AND THIRD SEPARATE DUCTS FORMED IN ITS INNER SURFACE, SAID FIRST DUCT BEING IN CONTINUOUS COMMUNICATION WITH SAID FIRST ANNULAR 